Could not register TCP channel: System.Net.Sockets.SocketException (0x80004005): Only one usage of each socket address (protocol/network address/port) is normally permitted

I have observed the above error message a couple of times on windows xp machines when the test agent service is restarted. The service does not start due to this error and in test agent log file following stack trace is observed.

This error seems to indicate that the socket on which test agent wants to listen is not available, probably because the old socket was not closed properly by the underlying layers. To come out of this error, I just restart the machine & it works.